Label-free sorting of stem cell-derived cardiomyocytes via electrophysiological phenotype
Stem cell therapies hold great promise for repairing tissues damaged due to disease or injury. However, one of the major obstacles in translating stem cell biology into tissue replacement therapy will be the establishment of effective purification methods which specifically isolate the desired cells for implantation and exclude those which may have adverse effects on the performance of the implanted graft or the health of the patient. Previous stem cell tissue replacement studies in the heart have failed, largely due to poor electromechanical coupling of implanted cells with the heart. We are developing a new technology for cell purification which will enable us to specifically isolate functional heart cells from mixed stem cell populations. Rather than looking for a protein or genetic marker, as is conventionally done, our technology electrically stimulates flowing cells and examines their response. Muscle cells, such as those found in the heart, will twitch upon electrical stimulation, and this twitch can be measured with a sensitive electrode. As this technique does not introduce any fluorescent labeling molecules or genetic modifications to the cell, it is much safer than traditional cell purification methods. Furthermore, since this functional test is closely related to the task that cells must perform in the heart (namely, contract in an organized, controllable manner), it is expected that cells purified in this way will form better tissue grafts. This proposal represents the first attempt to sort cells based on a dynamic, functional response to stimulus. As many of the cell types relevant for regenerative medicine are electrically-excitable (e.g. heart cells, brain cells, and blood vessel cells), this technology is also applicable to a variety of other neurodegenerative and cardiovascular therapies. The proposed system utilizes a microfluidic device with integrated electrodes for electrical stimulation and recording of extracellular field potential signals from suspended cells in flow. By combining hundreds or thousands of these tiny microdevices on a single chip, we can achieve throughputs relevant for clinical applications.
Cardiovascular disease (CVD) affects more than 1.7 million Californians and 71 million Americans. The societal and financial impacts are tremendous, with CVD accounting annually for an estimated $8 billion in CA and nearly $400 billion in US health care costs. In the case of chronic illnesses such as CVD, the state and national health care systems may not be able to meet the needs of patients or control spiraling costs, unless the focus of therapy switches away from maintenance and toward cures. CVD is typically caused by a loss in heart muscle. Once this heart muscle is gone, the body is not able to replace it. With the discovery of induced pluripotent stem cells, we may one day be able to create replacement heart tissue grafts derived from a patient's own cells, free of the ethical controversies and immune rejection issues associated with human embryonic stem cells.
We believe that the objectives of our research will benefit the people of California by addressing a specific bottleneck in the translation of stem cell biology to clinical tissue replacement therapies for the heart and other organs. The development of these tissue replacement therapies will require radically new methods for the cultivation and purification of stem cell-derived heart cells, and we believe that purification based on a functional assessment has the potential to produce highly pure populations in a safe, effective manner.
With the passage of Proposition 71 in 2004 and the creation of the California Institute for Regenerative Medicine (CIRM), California has positioned itself to remain at the forefront of stem cell research. We believe that the results of our work will lead to marketable tools and technologies which will generate royalties, patents, and licensing revenues for the state economy. Furthermore, the development of tools which enable cures for diseases such as CVD would improve the California health care system by reducing the long-term health care cost burden of these diseases. Our previous work has shown a commitment to developing practical technologies suitable for the marketplace, including the establishment of four companies from alumni of our research lab.
We have assembled a multi-disciplinary team to attack the objectives of our proposed research with expertise in microfluidic device development, electronic instrumentation, stem cell biology, and regenerative medicine. At the same time, we will train and mentor a new generation of bright students and junior scientists in the areas of technology development, regenerative medicine, and iPSC biology. This will ensure that an essential knowledge base will be preserved and passed on to both investigators and patients within and beyond California.